"We have only one responsibility: to tell the truth."
What is he on about? You'll see fly-by-night authors banging on about the truth all the time, spouting off about how their story shows a universal truth. But I've read their books and, I can tell you, hardly anyone dies and there is nothing in there about taxes.
These people are trying to trick you, or maybe they're on mad badger drugs. The truth is boring and cruel. If you write about the truth you'll get a story about a boy who isn't a wizard, going to school. Or a girl who goes to school and doesn't have amazing powers and doesn't get adopted by the lovely (and, in the film, hot teacher). The mice won't talk, they'll die painful deaths after eating poison. The lovely black horse will be boiled into glue. Danny's dad will be banged up and he'll be put in a home. The naughtiest girl in the school will get expelled. The pig would eat the spider then get turned into bacon. The Hardy boys would be found floating dead off the coast as a warning to other meddling kids...
It goes on.
So whatever you do, don't write the truth. Make everything crazy and exciting and a big lie. Explosions should fill every page. Women should be hot and have awesome racks (this is what they mean by write for yourself). The men should wear no shoes and white vests. Cats should fly, dogs be detectives and caterpillars gangsters. Don't worry about the plot or meaning or anything like that, just avoid the boring truth. No one's interested.
All the best,